Fix issue with Android Emulator not started

[giorgosneokleous93]

• It seems that the flag '-t' is not being used anymore, not sure since when as I couldn't find any documentation

• To ensure that the API is installed we run the sdkmanager --install

• API Level used now is "android-29" - changed as running "android-21" as previously the emulator warns that the 21 emulator is significantly slower

• Use the -k flag as recommended from the avdmanager doc

• To find list of AVD's you can run 'sdkmanager --list'

The installation of the SDK should happen only once.

Closes Issue:
#11

(disclaimer: this is my first github action modification or any addition)

[vgaidarji]

@giorgosneokleous93 the problem with missing system image still exists. What were your testing steps?

docker build -t docker-android-emulator .
docker run docker-android-emulator

Warning: File /root/.android/.android/repositories.cfg could not be loaded.
[=======================================] 100% Unzipping... x86_64/encryptionkey
*************************************************************************
The "android" command is deprecated.
For manual SDK, AVD, and project management, please use Android Studio.
For command-line tools, use tools/bin/sdkmanager and tools/bin/avdmanager
*************************************************************************
Running /opt/android-sdk/tools/bin/avdmanager create avd -f -n android-29 -k system-images;android-29;google_apis;x86_64

Auto-selecting single ABI x86_64========] 100% Fetch remote repository...
Do you wish to create a custom hardware profile? [no] *************************************************************************
The "android" command is deprecated.
For manual SDK, AVD, and project management, please use Android Studio.
For command-line tools, use tools/bin/sdkmanager and tools/bin/avdmanager
*************************************************************************
Running /opt/android-sdk/tools/bin/avdmanager list avd

Available Android Virtual Devices:
    Name: android-29
    Path: /root/.android/.android/avd/android-29.avd
  Target: Google APIs (Google Inc.)
          Based on: Android API 29 Tag/ABI: google_apis/x86_64
PANIC: Cannot find AVD system path. Please define ANDROID_SDK_ROOT
emulator:Auto-config: -force-32bit (ANDROID_EMULATOR_FORCE_32BIT=true)
emulator:Android emulator version 26.0.3.0 (build_id 3965150)
emulator:Found AVD name 'android-29'
emulator:Found AVD target architecture: x86_64
emulator:argv[0]: '/opt/android-sdk/tools/emulator'; program directory: '/opt/android-sdk/tools'
emulator:Cannot find system image path. Please define ANDROID_SDK_ROOT
emulator:Auto-config: -engine classic (based on configuration)

All proposed changes in PR make sense, we just need to improve further the configuration to make sure emulator is starting. I had a local branch on one of my working machines where I progressed on this, but didn't have time yet to fully finish that work or push to remote :(

[giorgosneokleous93]

@vgaidarji I will close the PR if that's okay with you.